This Code of Practice will be updated when necessary by distribution of a replacement Part A and such other parts as are amended. Amended or additional parts of revised pages will be marked by a vertical black line in the adjacent margin. Issue Date Comments Part A August 1995 Original document. Part B August 1995 Original document. Part C August 1995 Original document. Part D August 1995 Original document. Part E August 1995 Original document. Part F August 1995 Original document. Part G August 1995 Original document. Part H August 1995 Original document. Part I Not used. Part J August 1995 Original document. Part K August 1995 Original document. Part L August 1995 Original document. Part M August 1995 Original document. _______________________________________________________________

Distribution Controlled copies of this Code of Practice should be made available to all personnel who are responsible for the design, installation, testing, maintenance and faulting of Rail Clamp Point Locks. _______________________________________________________________

Health and Safety Responsibilities

In issuing this Code of Practice Railtrack PLC makes no warranties, express or implied, that compliance with all or any of Railway Group Standards or Code of Practice is sufficient on its own to ensure safe systems of work or operation. Each user is reminded of its own responsibilities to ensure health and safety at work and its individual duties under health and safety legislation. _______________________________________________________________

1 Purpose This code of practice gives details of best practice in respect of rail clamp point locks. 2 Scope The contents of this code of practice apply to all rail clamp point locks emanating from

the former BR design.

3 Concept The design of the clamp lock mechanism is based on the principle of providing a means

of individually locking and detecting a pair of coupled point switch rails. It is designed to ensure that the closed switch rail is always placed, lock and electrically detected relative to its associated stock rail. This ensures positive locking of the switch rail to its associated stock rail.

The clamp lock has the advantages:

eliminates extended sleepers.

eliminates vulnerable rodding connections (especially when used in conjunction with hydraulic supplementary drives).

is tolerant of the effects of track gauge spread and switch creep.

has its own power unit mounted in a safer working environment.

is compact and easier to handle than conventional electrical point machines.

The mechanisms are not left or right handed so that the same units are suitable for either side of the track (except switch diamond layouts, where the switch rail brackets are handed).

The clamp lock was originally designed by British Rail in the late 1960s and remained largely unchanged until 1987; this version is known as the Mk 1 and used a body assembly fabricated from steel plates. In 1987, a design review resulted in a series of interim modifications; these became popularly known as the A6 modifications and were derived from the Mk 1 machines. In 1988, the Mk 2 machine was produced in response to the Design Review Committees findings. The Mk 2 is immediately distinguishable from the Mk 1 due to the body assembly being a one piece cast component; it is sometimes referred to as the Cast Body design.

The Mk 1 clamp lock was designed to be used on rail sections of 109lb, 110lb and 113lb flat bottom inclined (FBI). It could also be used on 113A flat bottom vertical (FBV) rail or 95lb bull head inclined (BH1) rail, and could be fitted to any point layout.

The Mk 2 clamp lock is designed to be used on a rail section of 113A flat bottom vertical (FBV) rail. It can also be fitted to rail sections of 109lb, 110lb and 113lb flat bottom inclined (FBI), 95lb bull head inclined (BH1) and 113A/UIC 54B. Standard fittings are available for most point layouts, although the Mk 2 cannot be fitted to a switch diamond with inclined rail and, in the case of UIC rail, is only available for the plain lead layout. Further UIC layouts will become available as the permanent way details are finalised, and reference should be made to the latest issue of drawing BRS SM 52200 for availability.

Further detail of the assembly is shown in Part D: Installation.

The standard clamp lock is not trailable.

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Rail Clamp Point Locks

2 R A I L T R A C K

Code of Practice

GK/RC0774 Issue One

Date August 1995

Page B 2 of 36

4 General Description

Figure B1 shows the standard layout. Each clamp lock machine is in two parts: one part attached to the stock rail and the other attached to the switch rail.

The part which is attached to the stock rail is known as the lock and detector mechanism assembly. It consists of a lock body unit, which incorporates a drive lock slide and electrical detection components, with adaptor blocks fitted between the body and the stock rail.

The part attached to the switch rail is called the switch bracket assembly. This carries a lock arm, detector blade and some packing for adjustment of the lock. The switch bracket assembly is designed so that the thrust comes midway up the switch rail to prevent twisting.

The lock arm and point detector blade fit together with the drive lock slide to move in and out of the body.

To operate one point end the following components are required:

Two clamp locks.

One centre thrust bracket assembly.

One tie bar (joining the two machines).

Two single acting hydraulic actuators.

One hydraulic power pack.

Associated hose connections.

The two clamp locks are designated LH (left hand) and RH (right hand) when looking towards the points in a facing direction.

Movement of the point switches is achieved by the operation of two hydraulic actuators, which are centrally mounted back to back on the centre thrust bracket. The actuators are connected by small-bore hoses to the hydraulic control unit, which is independently mounted adjacent to the track.

For each clamp lock, electrical detection of its switch rail position is effected by double-pole sealed limit switches. These limit switches are operated by two cam followers, which rest on two linear cams : an adjustable cam on the detector blade and a fixed cam on the drive lock slide. Points closed and locked contacts make in the limit switch when both cams are in the correct position, whilst points open contacts make when the detector has moved to a position corresponding to the minimum point opening. In addition, the opposite switch rail is held open and detected at a safe flangeway clearance opening (108mm for plain leads or 85mm for switch diamonds measured at the tip, equating to 105mm and 82mm respectively when measured at the lock arm).

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Rail Clamp Point Locks

R A I L T R A C K 3

Code of Practice

GK/RC0774 Issue One

Date August 1995 Page B 3 of 36

Figure B1

Point Identificationnumber on plate toBRS-SM 2463

Hose Connections

Connecting Rod for mechanicaldrives may be fitted on either side

Drive Lug

Sleeve Nut

Centre Thrust BracketAssembly

Switch RailBracket Assembly

Taper Packing

Electro-Hydraulic PowerPack to be located, asconvenient at the side ofthe track, on a Point RodRoller Base

A

Lock &Detector MechanismAssembly (Cast Body)

Cable to Detector

SECTION ON AA Hose connections to Actuators fromElectro-Hydraulic Power Pack at theside of the track Tie Bar